Package having peelable film

ABSTRACT

A package for extended storage and in-store display of fresh red meat is disclosed. Preferably the package is made by a vacuum skin packaging process wherein the forming web is a composite peelable film having a peelable oxygen barrier layer and an oxygen permeable skin layer which remains to enclose the product when the peelable film is removed after storing. A means and method for readily initiating the peeling process is provided by a combination of a manual pull tab and selected perforations of the forming web.

FIELD OF THE INVENTION

This invention relates generally to packages having a peelable film orseparable skin. Particularly, the present invention relates to vacuumskin packages wherein the barrier layer or layers may be peeled andseparated from the non-barrier layer or layers and to the packageconfiguration which provides easy initiation of the peeling process.

BACKGROUND OF THE INVENTION

Skin packaging can be classified as a vacuum forming process forthermoformable polymeric films. However, the term "vacuum skinpackaging" or VSP as it is referred to hereinafter, refers not to thefact that the thermoformable film is formed around the product by vacuumor differential air pressure which, indeed it is, but more to the factthat the product is packaged under vacuum and the space containing theproduct is evacuated. For a number of products there is a need for thefilm formed around each product to be a barrier to oxygen, air, andother gases.

In conventional skin packaging, a backing board which is porous or whichis perforated is used so that a vacuum may be drawn directly through thebacking board. In vacuum skin packaging processes, generally, a vacuumchamber with an open top is used. A product on an impervious backingboard is placed on a platform within the vacuum chamber. The opening tothe upper chamber is covered by a sheet of film which is clamped tightlyagainst the chamber to form a vacuum tight closure. The chamber isevacuated while the film is heated to its forming and softeningtemperature. The platform is then raised to drive the product into thesoftened film and air pressure is used above the film to force ittightly around the product. A similar type process is disclosed inFrench Patent No. 1,258,357 which issued to Alain G. Bresson on Mar. 6,1961.

In another version of vacuum skin packaging in the prior art, which isdisclosed in U.S. Pat. No. 3,491,504, which issued to W. E. Young et alon Jan. 27, 1970, heat softened film is physically moved down over astationary product and, with the use of differential air pressure, thesoftened thermoplastic film is molded onto the product.

In U.S. Pat. No. Re. 30,009, which was reissued on May 29, 1979 toRichard R. Perdue et al, a thermoformable or heat softenable film sheetis drawn by differential air pressure against the concave interiorsurface of the upper portion of a vacuum chamber, the film is thenheated by surface contact, and then, after evacuation of the chamber,air pressure is used to blow the film down over the product and againstthe backing board. The resulting package comprises the productpositioned on the backing board which is gas impervious. The product isheld on the backing board by the thermoformable film which has beenformed around the product in the exact shape of the product so that itappears to be an almost invisible "skin." The thermoformable film orforming web, as stated previously, is also gas impervious and usuallywill consist of a number of layers each of which performs a specificfunction. The layer in contact with the product and backing member willbe a sealing or heat sealable layer. An interior layer will typically bea barrier layer which comprises a vinylidene chloride copolymer or ahydrolyzed ethylene/vinyl-acetate copolymer, and the outer surface layerwill be an abuse layer to protect the barrier layer from scratches, pinholes, or from moisture attack.

In U.S. Pat. No. 3,574,642 which issued on Apr. 13, 1971 to CarlFrederick Weinke, a package for a method of packaging meats isdisclosed. The package includes an inner oxygen-permeable member whichmay be also gas flushed or evacuated. The package preserves thefreshness of the meat until the meat is ready to be marketed to theconsumer. For marketing, the outer wrapper is removed and the innerpackage is displayed to the consumer. Being oxygen-permeable, the innerwrapper admits oxygen to the interior of the package causing the freshmeat product to change to a bright red color which the consumerassociates with freshness. The inner pouch of the Weinke package mayconsist of polyethylene film and the outer pouch may be cellophane filmwith a coating of saran (vinylidene chloride copolymer.) Another patentshowing portions of fresh meat individually packaged in oxygen permeableplastic film and inserted into an outer container of impermeable film isU.S. Pat. No. 3,681,092 which issued to Oliver R. Titchnell et al onAug. 1, 1972.

Another prior art package is described in U.S. Pat. No. 3,713,849 whichissued to Paul E. Grindrod et al on Jan. 30, 1973. In the Grindrod et alpatent a fresh meat package having an outer oxygen impermeable laminawhich is readily and entirely peelable from an inner oxygen-permeablelamina is disclosed. The package includes means for initiating thepeeling separation along an edge of the package. The outer oxygenbarrier maintains meats in well preserved condition in spite of thepurplish color which has low consumer appeal. Shortly prior to displayfor sale to the consumer the outer lamina is removed by the retailer andthe product develops a healthy, bright red "bloom" due to the highoxygen through-put of the inner remaining film package. The materialdisclosed in Grindrod et al is a laminate of PVC/Saran and EVA/Saran.(EVA designates ethylene/vinyl-acetate copolymer and PVC designatespolyvinyl-chloride.) The EVA and PVC layers are the inner layers and atthe periphery of the package they are sealed together. The saran layerscan be readily peeled from the respective EVA or PVC layers withgripping tabs that are provided.

Yet another peelable package is shown in U.S. Pat. No. 4,055,672 whichissued on Oct. 25, 1977 to Arthur Hirsch et al. In the Hirsch et alpatent a semi-rigid preformed tray of oxygen impermeable material isformed, a metal product placed therein, and then the tray is sealedaround its upper periphery or flange area by a composite lid which hasan inner layer of oxygen impermeable material, an adhesive layer, and anouter layer of oxygen impermeable material. When the package is readyfor retail display, in order that oxygen can reach the fresh meatpackaged within impermeable material, the outer, impermeable lid ispeeled away so that the oxygen can penetrate through the remainingportion of the lid. Accordingly, another object of the present inventionis to provide a package with a strippable or peelable barrier layerwhich is an improvement over prior art packages.

In a number of instances in order to preserve a meat product within animpermeable film, it is desirable to provide a modified atmosphere whichmay include inert gases such as nitrogen or the like or an atmospherewhich has a mixture of gases such as oxygen and carbon dioxide tocontrol the bacterial growth within a package. Typical packages aredisclosed in U.S. Pat. No. Re. 27,872 which issued on Jan. 8, 1974 to J.J. Estes; U.S. Pat. No. 2,623,826 which issued on Dec. 30, 1952 toSanford R. Grinstead; U.S. Pat. No. 3,360,382 was issued on Dec. 26,1967 to H. V. Miller; U.S. Pat. No. 4,522,835 which issued on June 11,1985 to Richard E. Woodriff; U. K. Patent No. 1,199,998 which waspublished July 22, 1970; Canadian Patent No. 890,766 which issued Jan.18, 1972 to Charles M. Davison et al; U. K. Patent No. 1,378,140 whichwas published Dec. 18, 1974; and in U. K. Patent No. 1,186,978 which waspublished Apr. 8, 1970. U.S. Pat. No. 2,925,346 which issued Feb. 16,1960 discloses a process of packaging cured meat products and inhibitingcolor degradation by removing oxygen and back filling the container witha gaseous oxide of nitrogen. Accordingly, it is another object of thepresent invention to provide a vacuum skin package which is suitable forand can be used with modified atmospheres.

In order to readily open packages where plastic film layers have beensealed together to close the package, various tear tabs and easy openmechanisms have been devised. One such easy-open, delaminating seal isdisclosed in U.S. Pat. No. 4,638,913 which issued on Jan. 27, 1987 toMilton A. Howe, Jr. In this patent, two grippable film folds areprovided to act as gripping tabs and the folds, when pulled apart, willrupture one of the outer layers of the sealed together film anddelaminate the film to its edge. In such a case, of course, the bondstrength between the two sealed together films must be greater than thelayer-to-layer bond strength of the film. Accordingly, it is stillanother object of the invention to provide a package which it is readilyopenable.

The foregoing and other objects are achieved by the present inventionwhich is described in the Summary of Invention below, and an embodimentof which is shown in the attached drawings, and which is furtherdescribed in the detailed description. The advantages of the inventionwill become apparent to those skilled in the art upon reading thisdisclosure which is understood not to be limited to the embodimentsdescribed herein.

SUMMARY OF THE INVENTION

In one aspect, the present invention is a package having a peelable filmlayer comprising a product; a support web upon whose upper surface theproduct rests, said support web having at least one edge; a compositefilm enclosing the product, said composite film comprising: a skin layersealed to the support web around the periphery of the product; and, apeelable layer coextruded with or laminated to the skin layer on theouter side of the package, the bond strength between the peelable andskin layers being of such strength that the two layers may be manuallydelaminated one from the other, said bond strength being less than theseal strength between the skin layer and support web; a header stripsealed to the upper surface of the support web adjacent an edge thereof;said composite film being superimposed over said strip but not adheredthereto, both the header strip and the composite film terminating at theedge of the support member whereby the composite film is readilyseparable from the header strip at said edge thereby forming a manuallygrippable pull tab; a series of perforations in the composite filmarranged substantially in a line generally parallel to the edge of theheader which is nearest the product, each perforation extending throughthe composite film and said line being located immediately adjacent tosaid header; the resistance of a peelable layer to tearing along theline of perforations being greater than that of the skin layer wherebywhen the pull tab is manually lifted the peelable layer will not tearalong said line but the skin layer will tear as it remains sealed to thesupport web while the peelable layer is peeled away.

In another aspect, the present invention is a package having a peelablefilm layer comprising a product; a semi-rigid support on a lower web ofthermoplastic material having a gas barrier coating or layer; a foamingweb which has been formed by a vacuum skin packaging process around theproduct and sealed to the lower web around the periphery of the product;said forming web comprising: a multilayer skin film comprising thesurface of the forming web which is sealed to the support web, said skinfilm being gas pervious; a multilayer peelable film, said peelable filmhaving a gas barrier layer; the bond strength between the skin film andthe peelable film being less than the bond strength between the skinfilm and support web and being weak enough to allow manual peeling ofthe peelable layer from the skin layer, non-stick means disposed alongan edge of said support member for preventing sealing of the forming webto the support web and the area of said means whereby the unadheredforming web forms a manual pull tab; and, peel initiating meansdistributed adjacent to and along the length of the non-stick means onthe side of said non-stick means opposite said edge, said peelinitiating means initiating the rupture of the portion of said skinlayer superimposed over the non-stick means from the remainder of theskin film whereby when the pull tab is pulled away from the support webthe peeling of the peelable layer from the skin layer is initiated.

In still another aspect, the present invention includes a vacuum skinprocess wherein a product is packaged between a forming web and asupport web wherein the improved method of initiating the forming webhas a peelable film layer with a peeling process comprising the steps ofproviding a non-stick surface adjacent to one edge of the support web;providing a forming web having manually separable layers comprising apeelable barrier film and a gas pervious film wherein the rupturestrength of a skin film is less than that of the peelable film; forminga vacuum skin package with the forming web sealed around the peripheryof the product to the support web, the product being spaced apart fromthe non-stick surface in the unsealed portion of the forming web overthe non-stick area thereby forming a manual pull tab, the seal strengthof the skin film to the support web being greater than the rupturestrength of the skin film; and, perforating the forming web with aplurality of perforations in a line adjacent to the non-stick surfacewhereby when the pull tab is manually pulled away from the supportmember the skin film ruptures leaving the peelable film free to bepeeled off the skin film.

DESCRIPTION OF THE DRAWINGS

Appended hereto and made a part of this disclosure are drawings ofillustrative embodiments of the invention in which:

FIG. 1 is a partial cross section in perspective of a package whichrepresents one embodiment of the present invention and shows themanually grippable pull tab;

FIG. 2 is the same view as FIG. 1 but illustrates the beginning of thepeeling operation;

FIG. 3 is a schematic representation of a top plan view of an array ofpackages made according to the present invention as they move from avacuum packaging station to a severing station, the packages beingarranged on a support web in rows and columns;

FIG. 4 is a blow up of a section from FIG. 3;

FIG. 5 is a schematic representation of the edge of a packageimmediately prior to the perforation operation;

FIG. 6 is a continuation of the perforation process shown in FIG. 5 andrepresents the preferred depth of penetration of the perforating knifeor member;

FIG. 7 shows a column of packages with the arrays of perforationsadjacent the pull tab of each edge of the packages; and,

FIG. 8 is a top plan view of one of the packages from the column shownin FIG. 7 having been severed to be an individual package.

DETAILED DESCRIPTION

Looking first at FIG. 1, one embodiment of the present invention isrepresented by package 1. Package 1 comprises a supporting member orsupport web 2 on which product 8 has been placed. The product ispreferably a cut of fresh red meat such as beef, lamb or veal and inmost embodiments will be a beef cut such as a filet or beefsteak.

The support web 2 or backing member can be a flat, sheet ofthermoplastic material, preferably polyvinyl chloride with a coating ofa vinylidene chloride copolymer which is commonly known as saran. Any ofthe vinylidene chloride copolymers which are good barriers to gas can beused included the vinyl chloride comonomer and the methyl acrylatecopolymer. The shape of the support web 2 is illustrated as being flatbut can be formed into a tray.

Draped over and closely conforming to the shape of the product 8 is thecomposite film 3 which is hermetically sealed to the support web 2around the periphery of the product 8 to enclose the product in agas-tight manner. A preferred method of forming the composite film orweb 3 over and around the product 8 and into a hermetically sealedcondition with the support web 2 is to use a vacuum skin packagingprocess preferably as disclosed in U.S. Pat. No. Re. 30,009 mentionedabove. When the composite film 3 is formed over the product 8 in avacuum skin packaging process the composite film 3 is referred to as theforming web.

The composite film or forming web 3 comprises a peelable film 4 and askin film 5 or sealable film. The skin film 5, as can be seen in FIG. 1,is sealed directly to the backing web 2. The peelable film does notcontact the support web 2 as its function is to provide a removable gasbarrier which will allow oxygen to penetrate the remaining skin film 5and produce a bloom on the beefsteak product 8 in the manner disclosedin the above mentioned U.S. Pat. No. 3,574,642.

The barrier film or peelable film 4 is preferably a multilayer gasimpermeable film comprising a plurality of layers including a barrierlayer comprising a material selected from the group consisting ofhydrolyzed ethylene/vinyl-acetate copolymers (EVOH) and vinylidenechloride copolymers (PVDC). A specific forming web which has been foundsatisfactory and is the best mode structure of a forming web at the timethis application is being filed is a forming web which is separable intothe permeable skin layer 5 and impermeable peelable layer 4 which havedetailed construction features as follows:

    __________________________________________________________________________    Skin or Sealing Layer 5                                                        ##STR1##                                                                     Wherein:                                                                      Sealant = VLDPE fron Union Carbide, or,                                       EVA Copolymer having 4% to 12% VA from duPont                                 Core = VLDPE, or,                                                             EVA Copolymer having 18% to 28% VA content                                    Optical = ULDPE from Dow, resins 4002A or 4002B                               Peelable layer 4                                                               ##STR2##                                                                     Wherein:                                                                      EVOH = Ethylene/vinyl-alcohol from Evalca                                     LDPE(tie) = Adhesive, preferably binell from duPont                           EVA = EVA copolymer having 18% VA                                             HDPE = High Density Polyethylene from USI                                     __________________________________________________________________________

In the preferred peelable film above it is seen that in order to achievevery good barrier properties two layers of EVOH are employed. The firstEVOH layer is the interface layer with the ULDPE layer in the sealantfilm 5. The interface layers; EVOH and ULDPE, are relativelyimcompatible polymers and when coextruded together form a very weakinterface and can be readily peeled apart.

To make the composite film or web, a coextrusion process similar to thatdescribed in U.S. Pat. No. 4,287,151 to Esakov et al on Sept. 1, 1981may be employed. Suitable annular multilayer dies must, of course, beused and these are well known to those familiar with the art ofcoextruding multilayer thermoplastic films.

The preferred film described above will seal to a saran coated PVCsupport web with a bond strength greater than the strength required todelaminate the peelable film 4 from the skin film 5 as in FIG. 2.

Turning now to FIG. 3, a vacuum skin packaging chamber 10 is representedon the right hand side and a severing or cutting station 11 isrepresented on the left hand side of FIG. 3. Prior to entering thevacuum skin packaging station 10 the products 8 have been arranged inrows and columns on support member 2 prior to entering the station 10where a vacuum skin packaging process, preferably according to themethod described in U.S. Pat. No. Re. 30,009 mentioned above, isemployed. Also, another patent publication which discloses product beingplaced on a support member, vacuum skin packaged, and then cut andsevered from the support web is UK No. 2,130,166 granted on Dec. 17,1986.

In the present invention, once the product is loaded onto the supportmember 2 in rows and columns as shown in FIG. 3 and prior to enteringthe vacuum skin packaging chamber 10, a strip of tape 6 has been putdown transversely across the support member 2 between each column ofproducts 8. This film which has an adhesive surface to stick to thesupport web 2 will have a non-stick upper surface which can be a surfacewhich has a coating of wax, Teflon, or similar material to which theskin or sealing film 5 will not adhere during the vacuum skin packagingprocess. Thus, the packages 8 as they emerge from the vacuum skinpackaging chamber 10 will have a cross section which is schematicallyrepresented by the blow up in FIG. 4 where it can be seen that the tape6 is placed between the columns of packages 8 preferably on the centerline between these columns. As an alternate to using a tape a non-stickmaterial could be coated onto the film in this position such as a rollersimilar to a print roller making such a coating transversely across thesupport web 2.

The perforating step, hereinafter described in more detail, can beperformed prior to entering the severing station 11 or in conjunctionwith the severing process or a column of products 8 can be detached orsevered from the continuous support web 2 as shown in FIG. 7. The lineof perforations 17 are placed preferably in the manner shown in FIGS. 5and 6.

Looking now at FIGS. 5 and 6, perforating blades 15 carried by rack 14are shown poised above the forming web 3 in the area immediatelyadjacent to the non-stick strip 6 so that when the perforating needlesor blades 15 are driven downwardly penetration is made as shown in FIG.6 with the result that no penetration is made through the non-stick area6 but the penetration through the layers 4 and 5 is made completely allthe way into the support web 2. It has been surprisingly found that inorder to make an effective line of perforations as shown in FIGS. 7 and8 that the perforations have to be spaced apart from the non-stick strip6. Any suitable blade or needle or punch will serve the purposeincluding the use of a serrated knife as long as the small holes orperforations are cut into the package immediately adjacent the headerlabel or non stick strips 6. Because this film is not sealed over thenon stick strip 6 it will provide a gripping tab as illustrated in FIG.1.

Referring now to FIG. 1, the manual gripping tab 18 which has been foundas explained below is shown partially separated from the header ornon-stick tape 6 and the perforation line left by the action of theneedle or punch 15 is shown. When the tab 18 is pulled in the directionof the arrow in FIG. 2 the sealable film 5 ruptures in the area adjacentthe header 6 where the perforation 9 has been placed leaving sealedsegment 5 still sealed to the supporting web 2 and ruptured segment 5"forms part of a tear tab which, as it is further pulled and rotated inthe direction of the arrow, will delaminate the barrier or peelable film4 from the skin or permeable film 5. Thus, the product 8 is leftcompletely covered by the permeable skin film 5.

The line of perforations enhance the tear process and provides astraight line along which the tear takes place. The spacing and size ofthe holes is determined by the thickness of the film and the differentfilm compositions and such determination can be done by those skilled inthe art. For the thickness of film of the preferred forming web setforth above, a perforation distribution of 5 per inch with eachperforation being about 1/16 inch in width has proven satisfactory. Itappears that from the work done that smaller holes closer together workmore satisfactorily. Of course, it is necessary that the rupture or tearstrength of the perforated barrier film 4 be greater than that of theperforated sealable film 5. The line of perforations seems to accentuatethe difference in tear strength or rupture resistance and allows for aneasy tear. Thus, a beefsteak, for example, which was in a vacuum packageduring a storage period which could be 14 to 28 days during which timethe beefsteak was a purplish color will now bloom into its bright redcolor, usually within 30 minutes to one hour, after the peelable barrierlayer has been removed thus exposing the surface of the meat to oxygenas it permeates the film.

An alternate way of applying the perforations would be to use a serratedwheel which would be rolled across the column of packages at theappropriate area adjacent the header.

Also, the header could include instructions or other labelinginformation on the non-stick surface 7 as the package 1 with thepeelable film 4 striped off is the package that would be in the retaildisplay case at the supermarket.

Upon reading and becoming familiar with the disclosure herein,equivalent film combinations and package configurations will likelybecome evident or obvious to those skilled in the art. However, thepresent invention is to be limited only by the scope of the followingclaims:

I claim:
 1. A package having a peelable film layer comprising:(a) aproduct; (b) a support web upon whose upper surface the product rests,said support web having at least one edge; (c) a composite filmenclosing the product said composite film comprising:(1) a skin layersealed to the support web around the periphery of the product; and, (2)a peelable layer laminated or coextruded to the skin layer on the outerside of the package; the bond strength between the peelable and skinlayers being of such strength that the two layers may be manuallyseparated one from the other, said bond strength being less than theseal strength between the skin layer and the support web; (d) a headerstrip sealed to the upper surface of the support web adjacent an edgethereof; (e) said composite film being superimposed over said strip butnot adhered thereto, both the header strip and composite filmterminating at the edge of the support member whereby the composite filmis readily separable from the header strip at said edge thereby forminga manually grippable pull tab; (f) a series of perforations in thecomposite film arranged substantially in a line generally parallel tothe edge of the header which edge is nearest the product, eachperforation extending through the composite film and said line beinglocated immediately adjacent to said header; (g) the resistance of thepeelable layer to tearing along the line of perforations being greaterthan that of the skin layer whereby when the pull tab is gripped andlifted the peelable layer will not tear along said line but the skinlayer will tear as it remains sealed to the support web while thepeelable layer is peeled away.
 2. The package of claim 1 wherein theline of perforations is substantially straight.
 3. The package of claim1 wherein the support member is gas impervious.
 4. The package of claim3 wherein the peelable layer is gas impervious.
 5. The package of claim4 wherein the peelable layer comprises a plurality of layers ofthermoplastic material at least one of which is a gas barrier layer. 6.The package of claim 5 wherein the skin layer comprises a plurality oflayers of thermoplastic film and the skin layer has relatively highoxygen permeability.
 7. The package of claim 6 wherein the interior ofthe package which contains the product has been evacuated.
 8. Thepackage of claim 7 wherein the product is fresh meat products.
 9. Apackage having a peelable film layer comprising:(a) a product; (b) asemi-rigid support or lower web which is a base of thermoplasticmaterial having a gas barrier coating or layer; (c) a forming web whichhas been formed by a vacuum skin packaging process around the productand sealed to the lower web around the periphery of the product; (d)said forming web being formed by coextrusion and comprising:(1) amultilayer skin film comprising the surface of the forming web which issealed to the support web, said skin film being gas pervious; (2) amultilayer peelable film, said peelable film having a gas barrier layer;(3) the bond strength between the skin film and peelable film being lessthan the bond strength between the skin film and support web and beingweak enough to allow manual peeling of the peelable layer from the skinlayer, (e) non-stick means disposed along an edge of said support memberfor preventing sealing of the forming web to the support web in the areaof said means whereby the unadhered forming web forms a manual pull tab;said non-stick means comprising a header strip with a non-stick surface,and, (f) peel initiating means distributed adjacent to and along thelength of the non-stick means on the side of said non-stick meansopposite said edge, said peel initiating means initiating the rupture ofthe portion of said skin layer superimposed over the non-stick meansfrom the remainder of the skin film whereby when the pull tab is pulledaway from the support web the peeling of the peelable layer from theskin layer is initiated, said peel initiating means comprising a seriesof perforations that penetrate the forming web.